Researchers say the smallpox virus could be catastrophic for humanity and wipe out large swaths of the population.

Smallpox was eradicated in 1980 by the World Health Organization but samples still remain in laboratories at the Centers for Disease Control and Prevention, the Vector Institute in Russia and WHO.

In 2017, Canadian researchers were able to make a smallpox-like vaccine in a laboratory, raising concerns the virus could be used as a biological warfare agent.

In mid-February, researchers at the Kirby Institute published a study that said they ran a simulation of a bioterror attack using smallpox in the Asia Pacific region and discovered no way authorities could act quickly enough to prevent an epidemic.

Using mathematical modeling of smallpox transmission, the team simulated a worst-case, large scale bioterrorist attack in an exercise test, called "Exercise Mataika."

The scientists started the outbreak in Fiji.

"A first case of haemorrhagic smallpox occurs in a private hospital in Fiji, but the diagnosis is missed, as clinicians are not familiar with the disease," researchers say in an article published in Global Biosecurity. "It is not until multiple cases are reported to the Ministry of Health and Medical Services that smallpox is considered as a diagnosis."

In the simulation, the outbreak spreads to 200 people with a fatality rate of 40 percent, local health authorities become overwhelmed, WHO declares a global emergency, airports and shipping ports close down, vaccines arrive in Fiji, but the virus has already spread to other countries.

"Under these conditions, modelling shows it will take more than a billion doses and 10 years to stop the epidemic," they write.